Forging aluminum alloy disc wheels



Feb. 28, 1956 E. H HARMoN FORGING ALUMINUM ALLOY DISC WHEELS Filed OCT..18, 1954 2 Sheets-Sheet l 'IIIIIIIJIIIUII 28 INVENTOR.

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FORGIG ALUMINUM ALLOYA Dsc WHEELS Filed O01.. 18, 1954 2 Sheets-Sheet 2Bxl/ange used in making cooking utensils.

United States Patent Oilice 2,736,574 Patented Feb. 28, 1956 roRcrNGALUMINUM Amor ntsc wnnnts Edward H. Harmon, Westlake, Ohio, assigner toAluminum Company of America, Pittsburgh, Pa., a corporation ofPennsylvania Application Qctober 18, 1954, Serial No. 462,915

7 Claims. (Cl. 14S-42.7)

This invention `is concerned with the production of aluminum base alloyforged disc wheels for trucks, buses and other vehicles and it moreparticularly relates to forged wheels made of those alloys which must besolution heat treated and precipitation hardened to develop theirmaximum mechanical properties.

The design of wheels for automotive vehicles and the materials used intheir construction have undergone great change over the past halfcentury. Originally, the wheels were" of relatively large diameter withsmall hubs, long spokes and narrow rims. Wood was the major structuralmaterial. As the size and speed of the vehicles increased, smallerwheels were adopted and steel eventually replaced all of the Wood. Morerecently, the spoke type of wheel has been supplanted in large part bythe current disc design. Both the spoke and disc type steel wheels havebeen made in two parts, namely, the rim and the hub section withattached spokes or web. lt has been necessary, therefore, to assemblethe two parts and fasten them together, usually by riveting or othermechanical means. Such assembly work is of course expensive andintroduces the possibility of failure of the means used to join the twoparts.

The common metal employed for wheel .construction has been steel becauseof its strength and availability at relatively low cost. However, withthe demand for increased pay loads and the need for more effectivedissipation of heat especially in heavy duty service in truck and busoperation, attention has been given to the replacement of steel by othermetals. ln addition, from a fabrication standpoint, steel plate has notbeen adapted to the production `of deep drawn articles in a few steps.VIt has been found that a long series of operations are required to makedeep drawn steel products which, of course, increase their cost.

Solution heat treated and precipitation hardened aluminum base alloys,on the basis of their properties, offer distinct advantages over steelfor vehicular wheel construction. Such wheels are lighter in weight,have adequate strength and possess a higher thermal conductivity thansteel, the last named property being particularly advantageousindissipating heat generated both from brakes and tires. However, thefabrication of such wheels has presented d iflicult problems since thestrong aluminum base alloys cannot be readily bent and drawn to adesired shape as is the case with non-heat treated alloys Furthermore,to forge the wheels according to conventional procedure would require atleast five or six working operations with a corresponding number of diesand the labor incident to lhandling of the wheel between the variousstages of fabrication.

My invention is directed to a method of making deep drawn aluminum baselalloy forged disc wheels inthe solution heat treated and precipitationhardened temper. One of the objects of myinvention is to provide amethod Qfhot ,Shaping aluminum alloy wheels whereby a minimuni amount ofmetal is wasted through trimming and punching. Another object is toprovide a fabrication procedure which can utilize various types ofworked aluminum alloy stock. A further object is to provide a method offorging wheels which gathers sufficient metal in the region of sharpbends to prevent an undue thinning out or weakening of the wheel. Aparticular object is to provide a forging method which permitsproduction of a wheel shape in only two drawing steps. Another specialobject is to integrate the heat treatment of the aluminum alloy forgedwheel with the drawing operations whereby the finished-wheel isdimensionally accurate, free from warpage and possesses the requisite ofhigh strength. It is also an object of my invention to provide a methodof fabricating `forged aluminum alloy wheels which includes a slightamount of cold working in the final shaping operation.

The foregoing objects and others are realized in my method of makingforged disc wheels which is more particularly described in the followingspecification and illustrated in the accompanying figures where Fig. lis a side View of a flat circular plate.

Fig. 2 is a cross sectional View of a shaped disc forged from thecircular plate.

Fig. 3 is a sectional view of the forged disc in position between thepunch and die before the rst pressing operation.

Fig. 4 is a sectional view of the same punch and die upon completion ofthe pressing operation.

Fig. 5 is a sectional View of a second punch and die at the end of thesecond pressing operation.

Fig. 6 is a sectional view of the die and punch used to stretclrandstraighten the wheel after it has received a solution heat treatment andhas been quenched, and

Fig. 7 is a perspective view of the finished forged wheel.

The method of forging heat treatable aluminum base alloy disc wheelsaccording to my invention broadly consists in first providing a circularwrought plate of suitable thickness, forging the circular shape into ashaped disc, hot pressing the disc to substantially the maximum requireddepth, subjecting the thus shaped cup to a further pressing to develop adetailed Wheel shape, solution heat treating the drawn product.quenching it, straighteningand .stretching the quenched article at roomtemperature and finally precipitation hardening the wheel. Each of theforegoing steps contributes to developing the required sectionalthickness, shape and properties of the final product. The finished wheelis of one piece construction and can be of a depth which is more than ofthe diameter. This is a greater depth than has been produced in anysteel disc wheel with which I am acquainted. Solution heat treated andprecipitation hardened wheels made in accordance with my invention havesuch typical mechanical properties as 68,000 p. s. i. tensile strength,57,000 p. s. i. yield strength, 13% elongation, a Brinell hardness ofand an endurance limit of 18,000 p. s. i. In addition, these wheels areof lighter weight than steel wheels used for the same service andtherefore reduce the unsprung load of the vehicle.

The aluminum base alloys employed for the production of forged discwheels should be of the type thatrequires solution heat treatment andprecipitation hardened to develop a high strength. A variety of suchalloys are available, the choice of any one being dependent on theparticular properties desired and ease of working. Broadly speaking,alloys of the aluminum-copper-magneslum-manganese,aluminum-magnesium-silicon or aluminum-Zinc-magnesium-copper types areadapted to being forged. It has been found that those alloys of the rsttype possess kthe best combination of forging characteristics andultimate strength properties. In particular, two alloys have been-foundto be very successful, namely, onecomposed` of 3.9 to 5.0% copper, 0.5to 1.2% silicon,

0.4 to 1.2% manganese, 0.2 to 0.8% magnesium and balance aluminum andimpurities; and the other composed of 3.8 to 4.9% copper, 1.2 to 1.8%magnesium, 0.3 to 0.9% manganese and the balance aluminum andimpurities.

The alloys may be fabricated to convenient plate form by anyconventional hot working method, such as by rolling, forging, pressingor by extrusion. Rolled plate is generally the most convenient andcheapest form of stock to use. The plate is fabricated to a thicknessslightly greater than that of the major portion` of the subsequentlyforged disc. Circles or similar shapes may be cut from such plate stockby any conventional method. The diameter and thickness of the wheelstock should be great enough to permit the formation of some ash at theperiphery of the disc and thus insure complete lling of the disc formingdies as well as obviating the need for a careful cutting of the stock toexact dimensions.

In the first step of my forging procedure the circular plate is heatedto a suitable forging temperature, usually between 650 and 950 F. in thecase of the aluminumcopper-magnesiom-manganese type of alloy it ispreferred to preheat the circle to a temperature between 800 and 880 F.

The preheated circular plate is to be transferred immediately to aforging press or hammer and the plate is converted into a disc ofpredetermined contour between appropriately shaped dies. l prefer to usethe hammer type of forging equipment inasmuch as this produces a quick,thorough working of the metal over the entire disc and distributes thestock, filling all of the recesses in the dies.

The shape of the forged disc is of paramount importance in securing aproper distribution of the metal necessary for effecting subsequentdrawing operations without undue thickening or reduction in thickness ofthe drawn product. The forged disc is of varying thickness in the radialdirection from the edge to the center. Generally speaking, the edge andadjacent portion of the disc is of substantially lesser thickness thanthe plate from which the disc was formed. rihe section thicknessincreases gradually in the radial direction from the edge to an annularcheek portion which is located approximately midway between the edge andthe center of the disc, but the thickness of portion between the edgeand cheek is still less than that of the wrought plate. One surface ofthe disc, which eventually forms the inside of the wheel body, issubstantially flat and in one plane over the distance from the edge to aline opposite the inner edge of the cheek section. From that line thesurface gradually dips toward the center thus forming a slightdepression. On the other side of the disc the surface is flat for ashort distance inwardly of the edge and up to the cheek portion.However, the Hat portion is not parallel to the surface on the oppositeside of the disc but is at a slight angle thereto, the surface risingfrom the edge toward the cheek and merging therewith. lf desired theedge may be rounded into this surface. The annular cheek portion,referred to above, is of a thickness greater than that of the initialcircular plate and has a greater cross section than the portions of thedisc on either side of it. The cheek section eventually provides metalat the major right angle bend in the wheel between the web or boltflange and the wheel rim. The enlarged cheek portion appears on but oneside of the disc in the form of a gently rounded annular ridge. Thewidth of the ridge or cheek will vary with the depth of the draw and theseverity of the bend, but generally this will be between about and 35%of the radius of the disc. The surface of the disc in the central part,i. e. the area circumscribed by the annular cheek, is substantially atand in a single plane. This area is opposite the depression on the otherside of the disc. As a result, the central portion of the disc is ofreduced thickness and less metal is wasted in punching the hub hole thanwould otherwise be the case. Shaping of the disc in the foregoing mannertends to eliminate any directional properties found in the plate and toestablish a radial ow of metal.

Ori completion of the disc forging operation the forged product isreheated to a suitable forging temperature within the range mentionedabove and then subjected to the first press forging operation. In thisstep the forged disc is drawn into a cup shape in a single step tosubstantially the depth of the final product. The space be tween thepunch and die is such as to provide a cup wall of slightly taperedsection from the top to the right angle bend portion, the top beingslightly thinner than the lower portion. The thickness of the section inthe bend between the bottom and sides of the cup should be of a greaterthickness than the portion on either side thereof to provide sufcientmetal for subsequent shaping operations. rihe bottom portion of thedrawn product can be of uniform thickness, at least over that portionwhich will eventually form the web or bolt flange.

The initially formed wheel shape produced by the foregoing operation isallowed to cool to room temperature and the hole for the wheel hub ismachined, punched or otherwise cut out. In addition any flash at theedge of the drawn product should be trimmed off.

In preparation for the next and nal drawing operation, the trimmed andpunched product is reheated to the forging temperature and thensubjected to the drawing operation. In this step the upper edge of thecup can be given any desired detailed shape such as one which willprovide a flange for retaining the tire on the finished wheel. A furthershaping and stretching at the major right angle bend can also beaccomplished and thus insure sufficient thickness of metal forsubsequent machining operations such as may be necessary to accommodatea tire retaining ange.

The product shaped in the foregoing step is next subjected to a solutionheat treatment. This consists of heating the article to a temperaturebetween about 850 and l000 F., the precise temperature and length oftreatment selected being determined by the composition of the alloy. Thepurpose of the treatment, as suggested by the term solution, is todissolve substantially ail of the soluble alloying elements. In the caseof the aluminum-c0ppermagnesiummanganesc type the treatment should bebetween 910 and 950 F. The wrought product should be held within theforegoing temperature range for a period of two to six hours but undersome conditions a longer or shorter period may be used depending on theheating means. Upon completion of the solution treatment the wheelshould be removed from the furnace orother heating medium and quenched,preferably in water, at to 160 F. lt is to be understood that otherquenching media may be used but water is ordinarily preferred because ofits ready availability and the severity of cooling which it provides.

The quenched article may be somewhat distorted by reason of the drasticchill and, in any case, it is necessary to bring the wheel to theprecise desired nal dimensions. For this purpose the quenched product iscold pressed or drawn with a slight increase in diameter of the wheel.This may mean a reduction in thickness of no more than l or 2%. Thestraightening and stretching introduces some cold work which thoughsmall is nevertheless advantageous from the standpoint of increasing thefatigue life of the wheel. The cold working appears to produce stresseswhich are opposite to those encountered in road service. Furthermore,the cold working, which is not uniform over the entire wheel body, takesplace Where fatigue is likely to occur.

The final step in the process is that of precipitation hardening thecold Worked wheel. Some aluminum base alloys harden sufficiently bystanding at room temperature for several days while it is necessary toheat others to a low temperature to achieve the desired" increase inhardness and strength. In the latter case, the treatnient is usuallycarried out Within a temperature range of 2.50 to 450 F. over a period Of 1 to 3.0 hours dsnendf ing upon the alloy. If analuminum-copper-magnesiumf manganese alloy is used of the compositionreferred to above, the hardening treatment is carried out at 340 to 400F. for a period of 5 to 15 hours. The hardened wheel is then ready forfinish machining operations.

1n using lsome aluminum b ase alloys it may be pos.- sible to elfectsuiiicient solution kof the soluble elements during preheating .toeliminate the need for a separate solution treatment providing theforged article is quenched from the forging die. When this is done the.quenched article is straightened and stretched as described above andfinally precipitation hardened.

Referring to the drawings the circular disc 10 shown in Fig. 1 is forgedto a shape illustrated in Fig. 2. In Fig. 2 the top -flat surface 13 ofthe disc 12 extends inwardly of the edge over a major portion of ltheradial distance from the rim to the center. Between the vrliat portionsis a depressed central area 15. The under side of the disc, whicheventually forms the exterior of the wheel, consists of slightly taperedsurface 18 which merges into the annular rounded cheek section 14. T hecheek is substantially midway between the edge and ythe center of thedisc and of a thickness greater than that of the plate from which it ismade. .Opposite the depression '1-5 and within the annular cheek sectionis another depression `16 lhaving a flat surface `19. It is from thisportion o f the disc that a hole s punched out to receive the vaxle hub.A tiash 2t) at the edge of the disc is s ubsequently trimmed.

The forged disc is drawn to the rst shape in a forging press having apunch and a die as seen in Fig. 3. The die body 22 has a cavity thereinhaving a vertical wall 24 with a beveled section 26 anda bottom 2 8. Thecavity,

it should be noted, has a depth of more than half Vits diameter. The dieis mounted in customary manner upon an anvil in a conventional forgingpress through the keyed section shown at the base of the block. Thepunch consists of `body 30 having a substantially vertical wall 32, butvwith enough draft -to permit Withdrawal ofthe punch, which blends intoan upper beveled surface 34. The punch fis supported from platen 42attached to the press ram, not shown. The bottom surface 36 of the punchmerges into the vertical surface 32 over a gradual curve. Means forknocking out the drawn article when the punch is raised is illustratedby `knock out plug 38, mounted on stem 4t) which passes upwardly throughthe -punch `body .and through the platen 42. The lower surface of theplug, it will lbe appreciated, forms a portion of the bottorn lpunchsurface during the drawing. The knock out assembly is operated byconventional means, not shown, which form a part of the forging press. Aknock out assembly consisting of plug 37 mounted on stem 41 can also tbeprovided in the die. To properly position the forged disc on die body 22four locating blocks 44 `are welded or otherwise attached to the topsurface of -the die adjacent the edge thereof but removed from the diecavity. To facilitate removal of the drawn article from .the punch aconventional stripper may be mounted in the `press which cooperates withthe punch in known manner.

The relative position of punch and die withrespect tothe forged disc atthe beginning of the pressing operation is to be seen in Pig. 3. At theend of the press ystroke the punch, die and pressed product 46 are inthe Lposition illustrated in `Eig. .4. The product 46 has a depth ofmore than 50% of the diameter of the cup.

The second drawing operation is performed with a similar punch and dieassembly Vwhich is more particularly illustrated in Fig. 5. Here -adieblock 48 is provided with a cavity having vertical wall 50 and contouredwalls 52 vand 5 4 which assist in forming the tire flange upon thewheel. The bottom surface 56 of the die cavity provides the desiredexternalcontour `of the bolt ange section of the wheel. l The punch body58 .has nearly vertical surface 6,0 with enough draft .for withdrawal ofthe punch and surfaces, 62 and 64, which are complementary to 5,2 and5.4, respectively, of the die cavity, Surface 66 together withfa portionof the bottom surface of plug 38 form the interior .of the base portionof the drawn article. The knock ont' plug 38 and stem 4.0 together withplaten 42 are identical` with those elements appearing in Figs. 3 and 4.A knock out plug 37 and stem 41 may also be provided in the .die body ina similar manner to that men.- tioned above in connection with the lirstpunch and die. The product of this .operation is the drawn body 68 whichhas a total depth only slightly greater than that of the precedingproduct 46.

The straightening and stretching of the wheel is done at room'temperature in .apparatus shown in Fig. 6. 1`he die body 78 is providedwith a cavity having a vertical surface 80 with contoured sections 82and 84 to accom.- modate the tire flange, la-.base surface 86 and aspecial corner shape 88. The punch body 90 has an almost verticalsur-,face 92 extending up to the platen 42. The surface 92 has a slightvdraft which aids in withdrawal of the punch. This surface also mergesinto flat bottom surface 84 over a gradual smooth curve. The same typeof knock out means, plug 38 mounted on stem 40, is employed in the punchwith plug 37 on stem 41 functioning in the die, as describedhereinabove. The product of this operation, identified as 96, has totaldepth substantially the same as that of the drawn article 68.

As an example of my process, I will now describe the forging of a wheelbody from an alloy having a nominal composition of aluminum, 4.4%copper, 0.8% silicon, 0.8% manganese and 0.4% magesium. This alloy inVthe form of hot rolled .plate l inch in thickness is heated toatemperature of between 800 and 880 F. whereupon it is removed from lthefurnace or other heating means and forged under a hammer vto the discshape .illustrated in Fig. 2. The section between surfaces 13 and 18 isslightl;I tapered because of the inclination of surface 18 and is of athickness varying between vabout 3/4 and 7A; inch. The `maximum cheekthickness, however, is about 1% inch. The central portion has a .minimumthickness of about .1/2 inch. The forging is then reheated to the sameforging temperature and hot .pressed with a punch kand die assemblyshown yin Figs. 3 and 4, the disc 12 being initially positioned on thedie 22 between the locating Ablocks 44. As the punch 30 descends vthedisc :bends andV assumes lthe shape seen in Fig. 4. It is .to be notedthat this shape 46 is substantially of the full depth of the wheel andthat the depth is more than 50% of the diameter. A yiiange section isdeveloped between the .beveled surfaces y26 ,and 34 of the die andpunch-respectively.

The initial drawn section 4 6 is allowed to cool to room temperature andhole 76 is punched out to accommodate the'axle hub. 4In addition, .theflash 20 on Vthe original disc 12 is trimmed oil.

The second and final pressing operation illustrated in Fig. 5 isaccomplished by heating .the vshape 4 6 4to the forging temperaturerange mentioned above and pressing it between die 48 and punch 58. Inthis operation the tire flange -is formed by bending the previous 'bevelange `of the -shape shown at 7 0 and 72 to form a right angle section.At the major bend 74, between the bolt flange and the tire rim a specialshape is given tothe wheel to provide enough metal `for subsequentmachining operations. In this .pressing the .depth of the cup is onlyslightly changed, the primary purpose being that of pro.- viding adetailed shape.

The hot pressed article 68 produced by the ,preceding operation isallowed lto cool to room temperature and vreheated to the solution heattreating temperature or it may be transferred directly from the forgingpress .to the heat treating furnace. Y,In -,any case, the wheel isheated t0 ,a temperature between .9.2.0 and v94.0" .foral ,hours andquenched innate-r at .14,0 to .F The qusnhed product which may beslightly warped is placed in die 78 and stretched and straightened bydownward movement of punch 90. The diameters of the die 'cavity and thepunch are slightly greater than those of the forging press with theresult that the diameter of the wheel is slightly enlarged. Thisintroduces a small amount of cold work which is beneficial to increasingthe fatigue life of the wheel. As the final step, the stretched andstraightened wheel body is precipitation hardened by heating it to about375 F. for ll hours. The forged wheel when removed has the shapeillustrated in Fig. 7, the tire rim and flange having a thickness on theorder of 1/2 inch and the bolt flange being about l inch in thickness.

Having thus described my invention and an embodiment thereof, I claim:

l. The method of making precipitation hardened deep drawn cup shapedforged disc wheels of heat treatable Valuminum base alloys comprisinghot forging rom fiat stock a contoured disc one surface of whichconsists of a substantially flat portion extending inwardly from theedge and merging into a central depressed area while the other andopposite surface consists of a at inclined portion adjacent the edge,said inclined portion extending upwardly toward and merging with anannular relatively wide rounded cheek section, and a substantially atcentral portion within said annular cheek section, said central fiatportion being opposite the depresed area on the other side of the disc,hot pressing said disc into a cup shape of substantially the depth ofthe final wheel with said at and depressed area surfaces forming theinterior surface of the cup, hot pressing said cup a second time tocomplete shaping of the wheel body, solution heat treating said wheelbody, quenching it, stretching said quenched body whereby the diameterof the wheel is slightly increased and the metal is cold worked andthereafter precipitation hardening said cold worked wheel body.

2. The method of making precipitation hardened deep drawn cup shapedforged disc wheels of heat treatable aluminum base alloys comprising hotforging from at hot worked plate a contoured disc one surface of whichconsists of a substantially llat portion extending inwardly from theedge over a major portion of the radial distance between the edge andcenter and merging with a depressed area occupying the central portionof said disc, the other and opposite surface of said disc consisting ofa at inclined portion adjacent the edge, said inclined portion extendingupwardly toward and merging with an annular relatively wide cheeksection substantially midway between the edge and the center of thedisc, and a flattened portion inwardly of said cheek section occupyingthe central area of said disc, said iiattened portion being oppositesaid depression on the other side of said disc, hot pressing said discinto a cup shape in a single operation, the depth of said cup beingsubstantially that of the final wheel, said llat and depressed surfaceforming the interior of said cup, cooling said cup, punching a hub holein the bottom of said cup, heating and pressing the cup into wheel form,solution heat treating the wheel body at a temperature between 850 andl000 F., quenching, straightening and stretching said` body whereby thediameter is enlarged and the metal is cold worked, and thereafterprecipitation hardening said wheel body.

3. The method of making precipitation hardened deep drawn cup shapedforged disc wheels of heat treatable aluminum base alloys comprisingheating at plate stock to the forging temperature between 650 and 950F., forging a contoured disc from said stock, said contoured disc havinga thickened annular section substantially midway between the edge andthe center of greater thickness than the original plate, the top surfaceof said forged disc being substantially at over the radial distanceextending inwardly from the edge to a line substantially opposite theinner edge of said thickened annular section, v.

said flat surface merging into a central depressed area,

the bottom surface of said disc consisting of an inclined flat portioninwardly of the disc edge, a raised relatively wide annular ridge and asubstantially hat central portion opposite said depressed area on theother side of said disc, press forging said disc at a temperaturebetween 650 and 950 F. into a cup shape so that the top at surface formsthe inner surface of the cup, said disc being drawn to a depthsubstantially that of the final wheel, cooling said cup, punching a hubhole in the bottom thereof, heating said cup to forging temperature,further press forging said cup to substantially final wheel form,solution heat treating said press forged product at a temperaturebetween 850 and l000 F., quenching to room temperature, cold workingsaid wheel by slightly enlarging its diameter and thereafterprecipitation hardening said wheel.

4. The method of making precipitation hardened deep drawn cup shapedforged disc wheels of heat treatable aluminum base alloys comprisingforging at 650 to 950 F. a contoured disc from at hot worked stock, onesurface of said disc consisting of a substantially hat annular portionextending inwardly from the edge and merging into a central depressedarea and the other and opposite surface consisting of a flat inclinedannular portion adjacent the edge, said inclined portion extendingupwardly toward and merging with an annular relatively wide roundedcheek section and a substantially at central portion within said annularcheek section, said annular cheek section being substantially midwaybetween the edge and the center of the disc and said central at portionbeing opposite the depressed area on the other side of the disc, hotpressing said disc at a temperature between 650 and 950 F. into a cupshape of substantially the depth of the final wheel with said fiat anddepressed area surfaces forming the interior surface of the cup, coolingsaid cup to room temperature and punching a hub hole in the bottomthereof, heating said cup to a temperature between 650 and 950 F. andfurther pressing said cup into the shape of a wheel body, solution heattreating said wheel body at a temperature between 850 and 1000 F.,quenching said pressed body in water below its boiling point, stretchingsaid quenched body whereby the diameter of the wheel is increased andthe metal is cold worked and there'.fter precipitation hardening saidcold worked wheel body at a temperature between 250 and 450 F.

5. The method of making precipitation hardened deep drawn cup shapedforged disc wheels of an aluminum base alloy composed of 3.9 to 5%copper, 0.5 to 1.2% silicon, 0.4 to 1.2% manganese, 0.2 to 0.8%magnesium and the balance aluminum and impurities comprising forging acontoured disc from plate stock at a temperature of 800 to 880 F., saidcontoured disc having one surface which consists of a substantially flatannular portion extending inwardly from the edge and merging into acentral depressed area and the other and opposite surface consisting ofa flat inclined annular portion adjacent the edge, said inclined portionextending upwardly toward and merging with an annular relatively widerounded cheek section and a substantially ilat central portion withinsaid annular cheek section, said annular cheek section beingsubstantially midway between the edge and the center of the disc andsaid central iiat portion opposite the depressed area on the other sideof the disc, hot pressing said disc at a temperature between 800 and 880F. into a cup shape of substantially the depth of the iinal wheel withsaid hat and depressed area surfaces forming the interior surface of thecup, cooling said cup to room temperature and punching a hub hole in thebottom thereof, heating said cup to a temperature between 800 and 880 F.and further pressing said cup into the shape of a wheel body, solutionheat treating said wheel body at a temperature between 920 and 940 F.,quenching said pressed body in water at 140 to 160 F., stretching saidquenched body whereby the diameter of the wheel is increased and themetal is cold worked and thereafter precipitation hardening said coldworked wheel body at a temperature between 340 and 400 F.

6. The method of making precipitation hardened deep drawn cup shapedforged disc wheels of heat treatable aluminum base alloys comprising hotforging from flat stock a contoured disc one surface of which consistsof a substantially at portion extending inwardly from the edge andmerging into a central depressed area while the other and oppositesurface consists of a flat inclined portion adjacent the edge, saidinclined portion extending upwardly toward and merging with an annularrelatively wide rounded cheek section, and a substantially iiat centralportion within said annular cheek section, said central flat portionbeing opposite the depressed area on the other side of the disc, hotpressing said disc into a cup shape of substantially the depth of thefinal wheel with said flat and depressed area surfaces forming theinterior surface of the cup, hot pressing said cup a second time tocomplete shaping of the wheel body, quenching said body from the die,stretching said quenched body whereby the diameter of the wheel isslightly increased and the metal is cold worked and thereafterprecipitation hardening saidk cold worked wheel body.

7. The method of making precipitation hardened deep drawn cup shapedforged dise wheels of heat treatable aluminum base alloys comprisingheating fiat plate stock to the forging temperature between 650 and 950F.,

10 forging a contoured disc from said stock, said contoured disc havinga thickened annular section substantially midway between the edge andthe center of greater thickness than the original plate, the top surfaceof said forged disc being substantially flat over the radial distanceextending inwardly from the edge to a line substantially opposite theinner edge of said thickened anvnular section, said flat surface merginginto a central depressed area, the bottom surface of said discconsisting of an inclined at portion inwardly of the disc edge, a raisedrelatively wide annular ridge and a substantially flat central portionopposite said depressed area on the other side of said disc, pressforging said disc at a temperature between 650 and 950 F. into a cupshape with said cheek section at the major bend between the vertical andhorizontal walls of the cup, the cup being drawn to a depth equal tomore than half the diameter of the cup, the top at surface of said discalso forming the interior of the cup, cooling said cup, punching a hubhole in the bottom thereof, heating said cup to a temperature between650 and 950 F., 4further press forging said cup to wheel form by forminga tire retaining right angle flange at the edge thereof, solution heattreating said flanged wheel at a temperature between 850 and l000 F.,quenching, cold working said wheel by enlarging its diameter andthereafter precipitation hardening said cold worked wheel.

No references cited.

1. THE METHOD OF MAKING PRECIPITATION HARDENED DEEP DRAWN CUP SHAPEDFORGED DISC WHEELS OF HEAT TREATABLE ALUMINUM BASE ALLOYED COMPRISINGHOT FORGING FROM FLAT STOCK A CONTOURED DISC ONE SURFACE OF WHICHCONSISTS OF A SUBSTANTIALLY FLAT PORTION EXTENDING INWARDLY FROM THEEDGE AND MERGING INTO A CENTRAL DEPRESSED AREA WHILE THE OTHER ANDOPPOSITE SURFACE CONSISTS OF A FLAT INCLINED PORTION ADJACENT THE EDGE,SAID INCLINED PORTION EXTENDING UPWARDLY TOWARD AND MERGING WITH ANANNULAR RELATIVELY WIDE ROUNDED CHEEK SECTION, AND A SUBSTANTIALLY FLATCENTRAL PORTION WITHIN SAID ANNULAR CHEEK SECTION, SAID CENTRAL FLATPORTIN BEING OPPOSITE THE DEPRESED AREA ON THE OTHER SIDE OF THE DISC,HOT PRESSING SAID DISC INTO A CUP SHAPE OF SUBSTANTIALLY THE DEPTH OFTHE FINAL WHEEL WITH SAID FLAT AND DEPRESSED AREA SURFACES FORMING THEINTERIOR SURFACE OF THE CUP, HOT PRESSING SAID CUP A SECOND TIME TOCOMPLETE SHAPING OF THE WHEEL BODY, SOLUTION HEAT TREATING SAID WHEELBODY, QUENCHING IT, STRETCHING SAID QUENCHED BODY WHEREBY THE DIAMETEROF THE WHEEL IS SLIGHTLY INCREASED AND THE METAL IS COLD WORKED ANDTHEREAFTER PRECIPITATION HARDENING SAID COLD WORKED WHEEL BODY.